I am having trouble with open captions staying in the position I have selected.
No matter how many times I set the font position bottom center it won't stick in most cases. I set each and every caption in my program to bottom center. I save and exit and reopen and the captions have repositioned without my intervention to the lower left.
This issue seems to be related to the horizontal size of the text block.
The wider the block, the less likely it will follow user selected formatting. Very long lines, those beyond title safety, can result in very bad final positioning. The real kick in the pants is text blocks may appear fine while you are editing them and then randomly change to a horrifying position.
The only means I was able to come up with to solve this problem was to shorten troubled caption blocks width to well within title safety. Then cut the text from the block, set center position via the user grid button, and paste the text back into the block.